I am playing around with the affiliate themes and I am wondering if it is possible for me to select certain products, categories, etc to show up for certain affiliates and not for others? This way I can have one affiliate ONLY show one category if i so choose.

Has anyone tried this?

This functionality does not exist out of the box. What you're describing sounds more like you want to have a "store" for each affiliate. Anyway, this is all possible with customization, of course, but it will take a fair amount of work.